Heat resistant film and metal laminate thereof

ABSTRACT

A heat resistant film comprising total 100 parts by weight of a resin composition comprising at least (A-1) a polyetherimide resin having repeating units of the structural formula (1), (A-2) a polyetherimide resin having repeating units of the structural formula (2), and (B) a polyarylketone resin having a melting peak temperature of 260 degrees C. or higher, and 5 to 50 parts by weight of a filler, wherein a weight ratio of the resin components, [(A-1)+(A-2)]/(B)], ranges from 70/30 to 30/70 and a weight ratio, (A-1)/(A-2), ranges from

FIELD OF THE INVENTION

This invention relates to a material used in the electronics industry,particularly to a heat resistant film suitably used for copper laminatedboards. Specifically, the present invention relates to a heat resistantfilm and a metal laminate thereof which film has good heat bondingproperty at a low temperature of 260 degrees C. or lower and goodbalance between edge tearing resistance and soldering heat resistanceafter a pressure cooker test.

DESCRIPTION OF THE PRIOR ART

A crystalline polyarylketone resin, typically polyetheretherketone, isexcellent in heat resistance, flame retardant property, hydrolysisresistance, and chemical resistance and, therefore, widely used mainlyfor aircraft parts, electric parts and electronic parts. However, rawmaterials for the polyarylketone resin are very expensive. Further, aglass transition temperature of the resin is so relatively low as about140 degrees C. to 170 degrees C. For this reason, various attempts havebeen made to further improve heat resistance of the resin, among which ablend of the resin with a noncrystalline polyetherimide resin hasattracted attentions.

The present inventor proposed a printed wiring board comprising theaforesaid blend and a production method thereof in Japanese PatentApplication Laid-Open No. 2000-38464 and Japanese Patent ApplicationLaid-Open No. 2000-200950.

A film comprising a composition comprising a mixture of the crystallinepolyarylketone resin and the noncrystalline polyetherimide resindescribed in aforesaid publications, which composition usually containsan inorganic filler to improve dimensional stability, has a controlledcrystallinity and a good heat bonding property at a low temperature of260 degrees C. or lower. A flexible printed wiring board made of thefilm has good dimensional stability and heat resistance.

However, mechanical strength, especially edge tearing resistance, of thefilm is not satisfactory, and folding resistance and bending resistanceare not enough to secure reliable electrical connection in the wiringboard. Further, improvement is required on handling property in aprocessing step of the wiring board.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a heatresistant film and a metal laminate thereof suitable as electronicmaterials, which film has good heat bonding property and good balancebetween edge tearing resistance and soldering heat resistance after apressure cooker test.

The present inventor has found that the above object can be attained bya heat resistance film composed mainly of a resin composition comprisinga crystalline polyarylketone resin and two specific noncrystallinepolyetherimide resins.

Thus, the present invention is a film comprising (A-1) a polyetherimideresin having repeating units of the following structural formula (1),(A-2) a polyetherimide resin having repeating units of the structuralformula (2), (B) a polyarylketone resin having a melting peaktemperature of 260 degrees C. or higher, and a filler in an amount offrom 5 to 50 parts by weight, based on total 100 parts by weight of(A-1), (A-2) and (B), wherein a weight ratio of the resin components,[(A-1)+(A-2)]/(B)], ranges from 70/30 to 30/70 and a weight ratio,(A-1)/(A-2), ranges from 70/30 to 30/70.

The weight ratio, [(A-1)+(A-2)]/(B), preferably ranges from 65/35 to35/65, more preferably from 65/35 to 45/55, and the weight ratio,(A-1)/(A-2), preferably ranges from 65/35 to 35/65, more preferably from65/35 to 50/50.

The amount of the filler preferably ranges from 10 to 45 parts byweight, more preferably from 20 to 40 parts by weight.

Another aspect of the present invention is a metal laminate comprisingthe above film and a metal body laminated on at least one side of saidfilm. Preferably, the metal body comprises copper, aluminum, orstainless steel.

Still another aspect of the present invention is a multilayered boardcomprising at least two copper laminated films, each comprising theabove film and a copper foil laminated on one side of said film.

Further, the present invention is a resin composition to prepare theabove film.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present film comprises (A-1) a polyetherimide resin having repeatingunits of the structural formula (1), (A-2) a polyetherimide resin havingrepeating units of the structural formula (2), (B) a polyarylketoneresin having a melting peak temperature of 260 degrees C. or higher, anda filler in an amount of from 5 to 50 parts by weight, based on total100 parts by weight of (A-1), (A-2) and (B), wherein a weight ratio ofthe resin components, [(A-1)+(A-2)]/(B)], ranges from 70/30 to 30/70 anda weight ratio, (A-1)/(A-2), ranges from 70/30 to 30/70. The term,“film”, as used herein also includes a sheet having a relatively largethickness of about 500 μm or larger.

The noncrystalline polyetherimide resin is a thermoplastic resin havingstructural units which comprises aromatic nucleus bonds, ether bonds,and imide bonds. Specifically, the noncrystalline polyetherimide resinsare those having the following repeating units (1) and (2), which areavailable under a trade name, “Ultem CRS5001” and “Ultem1000”,respectively, from General Electric Co.

The noncrystalline polyetherimide resin may be produced in any knownmethod. Usually, the noncrystalline polyetherimide resin of theaforesaid formula (1) is a polycondensation product of4,4′-[isopropylidene bis (p-phenyleneoxy)diphthalic dianhydride withp-phenylenediamine produced by a known method; and the noncrystallinepolyetherimide resin of the formula (2) is a polycondensation product of4,4′-[isopropylidene bis(p-phenyleneoxy)diphthalic dianhydride withm-phenylenediamine produced by a known method. The aforesaidnoncrystalline polyetherimide resins may include other copolymerizablemonomeric units in an amount which does not adversely affect the presentinvention.

The crystalline polyarylketone resin used in the present invention is athermoplastic resin having structural units which comprises aromaticnucleus bonds, ether bonds, and ketone bonds. Typical examples of thepolyarylketone resin are polyether ketone, polyetheretherketone, andpolyetherketoneketone, among which the polyetheretherketone of thefollowing repeating unit (3) is preferably used in the presentinvention. The polyetheretherketone having the repeating unit isavailable under trade names, “PEEK151G”, “PEEK381G”, and “PEEK450G”,from VICTREX Co. The crystalline polyarylketone resin can be used aloneor in combination of two or more of them.

A blending ratio in weight of the aforesaid noncrystallinepolyetherimide resins to the crystalline polyarylketone resin rangesfrom 70/30 to 30/70, preferably from 65/35 to 35/65, more preferablyfrom 65/35 to 45/55. A composition having a weight ratio higher than theaforesaid upper limit is undesirable because crystallinity of such acomposition as a whole is too low and crystallizes too slowly to attainsatisfactory soldering heat resistance, even though it contains thepolyarylketone resin having a melting peak temperature of 260 degrees C.or higher. On the other hand, a composition having a weight ratiosmaller than the aforesaid lower limit is undesirable, too, because aglass transition temperature of such a composition is too low to havesufficient dimensional stability and a circuit board made of thecomposition tends to shrink a lot due to crystallization and, therefore,is less reliable.

A blending ratio in weight of (A-1) the noncrystalline polyetherimideresin to (A-2) the noncrystalline polyetherimide resin ranges from 70/30to 30/70, preferably from 65/35 to 35/65, more preferably from 65/35 to50/50. A composition having a weight ratio higher than the aforesaidupper limit is undesirable because a multilayered board made by heatbonding such a composition tends to show blistering of the resin at aninterface between two layers in a pressure cooker test, herein afterreferred to as PCT. On the other hand, a composition having a weightratio smaller than the aforesaid lower limit is undesirable, too,because edge tearing resistance of such a composition is too small.

As the filler used in the present invention, any known filler can beused, for example, inorganic filler such as talc, mica, clay, glass,aluminum, silica, aluminum nitride, and silicon nitride, and fiber suchas glass fiber and aramid fiber. These may be used alone or incombination of two or more of them. The filler may be surface treatedwith a coupling agent such as titanate, fatty acids, resin acids, orvarious kinds of surfactants. Particularly when the present film is usedfor a printed wiring board, inorganic filler having an average particlesize of from 1 to 20 μm and an average aspect ratio, i.e., a ratio of aparticle diameter to a thickness, of about 20 to about 30 or larger,particularly 50 or larger, is preferably used.

The filler is incorporated in an amount of from 5 to 50 parts by weight,preferably from 10 to 45 parts by weight, more preferably from 20 to 40parts by weight, per 100 parts by weight of the aforesaid resincomposition. If the filler is incorporated in an amount larger than theaforesaid upper limit, flexibility and edge tearing resistance of a filmmay be undesirably lower. If the filler is incorporated in an amountless than the aforesaid lower limit, improvement in dimension stabilityattained by decrease in a coefficient of linear expansion is undesirablysmaller.

When the present film is used as a base material for an electronic boardsuch as a flexible printed wiring board, the film preferably has acoefficient of linear expansion of 30×10⁻⁶/degrees C. or smaller and anedge tearing resistance of at least 40 MPa, more preferably at least 50MPa, in both longitudinal and transversal directions. If the coefficientof linear expansion is larger than 30×10⁻⁶/degrees C., a laminate of afilm with a metal foil tends to curl or warp or to have insufficientdimension stability. A preferred range of the coefficient of linearexpansion depends on a type of the metal foil used, a circuit patternformed on the front and the back sides of the laminate, and the laminatestructure, but is generally from 10×10⁻⁶/degrees C. to 25×10⁻⁶/degreesC. If the edge tearing resistance is smaller than 40 MPa, reliability ofcircuit connection is insufficient in a thin board such as a flexibleprinted wiring board, or a handling property during processing of theboard tends to be bad. A measurement of the edge tearing resistance willbe described herein later.

These properties are obtained by subjecting the film to crystallizationtreatment. A method and a period of time for the crystallizationtreatment are not particularly limited, but may be, for example, a castcrystallization method where a film is crystallized when cast-extruded;an in-line crystallization method where crystallization is effected in afilm molding line, e.g., on a heat treatment roll or in a hot windfurnace; and an out-line crystallization method where crystallization iseffected off a film molding line, e.g., in a thermostatted oven or by ahot press. In the present invention, the out-line crystallization methodis preferably used in view of stability of production and uniformity ofthe properties. A time period of the crystallization treatment may suchthat the aforesaid equation is satisfied, and may be in a range of froma few seconds to a few tens hours, preferably from a few minutes toabout 3 hours.

In the present invention, any known method can be used for laminatingthe present film on a metal body such as a copper foil. Preferably, themetal body is heat bonded to at least one side of the aforesaid film bypressing them under heating without an adhesive layer therebetween.

Any known method can be used to heat bonding a metal body on a filmwithout an adhesive layer therebetween, for example, a method ofpressing a film and a metal body in a press heated to a desired heatbonding temperature, a method of heating a metal body to a heat bondingtemperature and pressing it onto a film, a continuous method of pressinga film and a metal body against each other on a hot rolls heated to aheat bonding temperature, and a combination thereof. When a press isused, it is preferred to employ a pressure per area of from 0.98 to 9.8MPa, i.e., 10 to 100 kg/cm², in an atmosphere of a reduced pressure ofabout 973 hPa so as to avoid oxidation of the metal. The lamination maybe made on one side of the film and the metal, or on both sides of thefilm and/or the metal.

Any known method such as etching may be used to form a conductivecircuit on the metal body of the present metal laminate for anelectronic board such as a flexible printed wiring board, rigid-flexibleboard, built-up multilayer board, bundled multilayer board, and metallicbase board. Any method can be used to form interlayer connection in amultilayer board, for instance, by plating through-holes with copper,filling through-holes or inner via holes with a conductive paste orsolder balls, or utilizing an anisotropically conductive materialcomprising fine conductive particles in an insulating layer.

The metal body to be used in the present invention may comprise copper,silver, gold, iron, zinc, aluminum, magnesium, nickel, or alloysthereof. These may be used alone or in a mixture of two or more of them.The metal may be surface treated with a surface treatment agent such asaminosilane, as far as the purpose of the present invention is notdisturbed.

The metal body may be in a form of a structural element, a strip to formelectric or electronic circuit, or a foil having a thickness of fromabout 3 μm to about 70 μm to form a circuit thereon by etching. Analuminum plate or foil is preferred mostly for heat dissipation; astainless steel plate or foil is preferred for an application where highcorrosion resistance, mechanical strength, or electric resistance isrequired; a copper foil is preferred for forming a complicated and finecircuit. Particularly one which is chemically treated, e.g., by blackoxidation treatment, is preferred. To increase bonding strength, asurface of the metal body to be bonded to a molded article of the mixedresin is preferably roughened chemically or mechanically before bonded.An example of such a roughened conductive film is a roughened copperfoil which has been electrochemically treated in the production ofelectrolytic copper foils.

The composition constituting the present film may comprise other resinsor various additives in addition to the inorganic fillers, such as heatstabilizers, UV absorbers, photo-stabilizers, nucleating agents,colorants, lubricants, and flame retardants, in such an amount that theydo not adversely affect the properties of the composition.

To mix the filler and various additives, any known method can be used.For example, (a) a master batch is prepared by incorporating theadditive at a high concentration, typically, of from 10 to 60 wt % in anappropriate base resin such as the polyarylketone resin and/or thenoncrystalline polyetherimide resin, and added to the resins to be usedto attain a desired concentration of the additive and then mechanicallyblended with a kneader or an extruder, or (b) the additive ismechanically blended directly with the resins to be used in a kneader oran extruder. Among the aforesaid mixing methods, the method (a) bypreparing and blending a master batch is preferred because higherdispersion and easier handling of the additive is attained. To improve ahandling property of the film, a surface of the film may be subjected toembossing or corona treatment.

The present film may be formed by any known method such as an extrusioncasting method using a T-die and a calendar method. Preferably, theextrusion casting method with a T-die is used, but not limited to it,because it allows one to make a film with ease and stable productivity.In the extrusion casting method using a T-die, a molding temperaturedepends on a flow property and film moldability of the composition butis generally in a range of from about a melting temperature of thecomposition to about 430 degrees C. The film usually has a thickness offrom about 10 to about 800 μm, but not limited to this.

EXAMPLES

The present invention will be explained with reference to the followingExamples, but not limited to them. Measurements and evaluation on thefilms described in the Examples were carried out as follows, wherein alongitudinal direction means a machine direction of an extruder and atransversal direction means a direction normal to the machine direction.

(1) Glass Transition Temperature (Tg) and Melting Peak Temperature (Tm)

These temperatures were determined from a thermogram obtained by heating10 mg of a sample at a heating rate of 10 degrees C./minute according tothe Japanese Industrial Standards, JIS-K7121, using DSC-7, exPerkin-Elmer Inc.

(2) Edge Tearing Resistance

According to the edge tearing resistance test specified in JIS C2151, atest specimen of 15 mm width by 300 mm length was cut out from a 75μm-thick film crystallized at a temperature of 250 degrees C. and at apressure of 2.94 MPa for 30 minutes, which conditions were the same asthose of vacuum pressing to make a multilayered board. The test specimenwas tested both in its longitudinal and transversal directions at adrawing speed of 500 mm/min using a test fixture B.

(3) Bonding Strength

The bonding strength was determined according to the method formeasuring a peeling strength of a film in its original state, asspecified in JIS C6481.

(4) Soldering Heat Resistance

In accordance with JIS C6481 for the soldering heat resistance test, amultilayered board was floated on solder in a bath at 260 degrees C. for20 seconds in such a manner that a copper foil side of the laminate wasin contact with the solder. After cooled to room temperature, the boardwas visually observed and evaluated for the presence of blisteringand/or peeling.

(5) Soldering Heat Resistance After Pressure Cooker Test

Using a pressure cooker tester, a multilayered board prepared wastreated at a temperature of 121 degrees C., a relative humidity of 100%RH and a pressure of 202650 Pa, i.e., 2 atm. After 4-hour treatment, themultilayered board was taken out from the pressure cooker tester. Then,the multilayered board was floated on solder in a bath at 260 degrees C.for 20 seconds in such a manner that a copper foil side of the laminatewas in contact with the solder, cooled to room temperature, and theboard was visually observed and evaluated for the presence of blisteringand/or peeling, according to JIS C6481.

Example 1

As shown in Table 1, a composition consisting of 30 parts by weight of(A-1) a polyetherimide resin (Ultem-CRS5001, ex General Electric Co.,having a Tg of 226 degrees C., hereinafter referred to as PEI-1), 20parts by weight of (A-2) a polyetherimide resin (Ultem-1000, ex GeneralElectric Co., having a Tg of 216 degrees C., hereinafter referred to asPEI-2) 50 parts by weight of (B) a polyetheretherketone resin (PEEK381G,ex Victrex Co., having a Tg of 143 degrees C. and Tm of 334 degrees C.,hereinafter referred to as PEEK), and 25 parts by weight of acommercially available mica (having an average particle size of 10 μmand an average aspect ratio of 50) was extruded into a film of 75 μmthickness at 380 degrees C. in an extruder provided with a T-die, andextrusion-laminated to a copper foil (18 μm thickness, surfaceroughened) to obtain a single side copper laminated film. For anevaluation purpose, a film of 75 μm thickness with no lamination wasalso prepared. From the single-side copper laminated film, testspecimens having an A4 size, i.e., 21 cm×29.7 cm, were cut out. On eachspecimen, a predetermined circuit pattern was formed by etching andthrough-holes were made which was filled with a conductive paste. Threetest specimens of single-side copper laminated film with theirthrough-holes filled with a conductive paste were stacked in the layeredstructure of copper foil/resin film/copper foil/resin film/copperfoil/resin film/copper foil and vacuum pressed at a temperature of 250degrees C. and a pressure of 2.94 MPa for 30 minutes to prepare amultilayered board. The evaluation results on the multilayered board areas seen in Table 1.

Comparative Example 1

A multilayered board was prepared in the same manner as in Example 1,except that a resin composition comprising PEI-1 and PEEK in aPEI-1/PEEK weight ratio of 50/50 was used instead of the resincomposition used in Example 1. The evaluation results on themultilayered board are as seen in Table 1.

Comparative Example 2

A multilayered board was prepared in the same manner as in Example 1,except that a resin composition comprising PEI-1, PEI-2 and PEEK in aPEI-1/PEI-2/PEEK weight ratio of 10/40/50 was used instead of the resincomposition used in Example 1. The evaluation results on themultilayered board are as seen in Table 1.

Comparative Example 3

A multilayered board was prepared in the same manner as in Example 1,except that a resin composition comprising PEI-2 and PEEK in aPEI-2/PEEK weight ratio of 50/50 was used instead of the resincomposition used in Example 1. The evaluation results on themultilayered board are as seen in Table 1. TABLE 1 Example ComparativeExample 1 1 2 3 PEI-1, part by weight 30 50 10 PEI-2, part by weight 2040 50 PEEK, part by weight 50 50 50 50 Mica, part by weight 25 25 25 25Edge tearing longitudinal 158.8 176.3 136.2 129.7 resistance transversal82.9 88.1 38.2 35.5 (MPa) Press temperature (° C.) 250 250 250 250Bonding strength (N/mm) 1.5 1.4 1.6 1.6 Soldering heat resistance GoodGood Good Good Soldering heat resistance after Good Not Good, Good Goodpressure cooker test Blistering observed

It can be seen from Table 1 that the film of Example 1 comprising thepolyarylketone resin and the two polyetherimide resins in a blendingweight ratio specified in the present invention has both good edgetearing resistance and good soldering heat resistance after the pressurecooker test on the film heat bonded at a low temperature.

On the other hand, the films comprising only either one of thepolyetherimide resins has a worse soldering heat resistance after thepressure cooker test on the film heat bonded at a low temperature as inComparative Example 1 or a worse edge tearing resistance as inComparative Example 3. The film of Comparative Example 2 comprising thepolyarylketone resin and the two polyetherimide resins specified in thepresent invention, but in a blending weight ratio outside the specifiedrange does not have good balance between the edge tearing resistance andthe heat resistance after the presser cooker test.

INDUSTRIAL APPLICABILITY

The present invention provides a heat resistant film and a metallaminate thereof, which film has an excellent heat bonding property at atemperature not higher than 260 degrees C. and a good balance betweenheat resistance after pressure cooker test and edge tearing resistance.The film and the metal laminated are suitable as a material forelectronic parts.

1. A film comprising (A-1) a polyetherimide resin having repeating unitsof the following structural formula (1), (A-2) a polyetherimide resinhaving repeating units of the structural formula (2), (B) apolyarylketone resin having a melting peak temperature of 260 degrees C.or higher, and a filler in an amount of from 5 to 50 parts by weight,based on total 100 parts by weight of (A-1), (A-2) and (B), wherein aweight ratio of the resin components, [(A-1)+(A-2)]/(B)], ranges from70/30 to 30/70 and a weight ratio, (A-1)/(A-2), ranges from 70/30 to30/70.


2. The film according to claim 1, wherein the amount of the fillerranges from 10 to 45 parts by weight, based on total 100 parts by weightof (A-1), (A-2) and (B), and the weight ratio, [(A-1)+(A-2)]/(B), rangesfrom 65/35 to 35/65 and the weight ratio, (A-1)/(A-2), ranges from 65/35to 35/65.
 3. The film according to claim 1, wherein the amount of thefiller ranges from 20 to 40 parts by weight, based on total 100 parts byweight of (A-1), (A-2) and (B), and the weight ratio, [(A-1)+(A-2)]/(B),ranges from 65/35 to 45/55 and the weight ratio, (A-1)/(A-2), rangesfrom 65/35 to 50/50.
 4. A metal laminate comprising the film accordingto claim 1 and a metal body laminated on at least one side of said film.5. The metal laminate according to claim 4, wherein the metal bodycomprises copper, aluminum, or stainless steel.
 6. A multilayered boardcomprising at least two copper laminated films, each comprising the filmaccording to claim 1 and a copper foil laminated on one side of saidfilm.
 7. A resin composition comprising (A-1) a polyetherimide resinhaving repeating units of the structural formula (1), (A-2) apolyetherimide resin having repeating units of the structural formula(2), (B) a polyarylketone resin having a melting peak temperature of 260degrees C. or higher, and a filler in an amount of from 5 to 50 parts byweight, based on total 100 parts by weight of (A-1), (A-2) and (B),wherein a weight ratio of the resin components, [(A-1)+(A-2)]/(B),ranges from 70/30 to 30/70 and a weight ratio, (A-1)/(A-2), ranges from70/30 to 30/70.
 8. A metal laminate comprising the film according toclaim 2 and a metal body laminated on at least one side of said film. 9.A metal laminate comprising the film according to claim 3 and a metalbody laminated on at least one side of said film.
 10. A multilayeredboard comprising at least two copper laminated films, each comprisingthe film according to claim 2 and a copper foil laminated on one side ofsaid film.
 11. A multilayered board comprising at least two copperlaminated films, each comprising the film according to claim 3 and acopper foil laminated on one side of said film.